US Robotics COURIER - Page 189

COURIER HIGH SPEED MODEMS
Characters Per Second
A data transfer rate generally estimated from the bit rate and the
character length.
For example, at 2400 bps, 8-bit characters with Start and Stop
bits (for a total of ten bits per character) will be transmitted at a
rate of approximately 240 characters per second (cps). Some
protocols, such as USR-HST and MNP, employ advanced tech-
niques such as longer transmission frames and data com-
pression to increase cps.
Class 1/EIA-578
An American standard used between facsimile application
programs and facsimile modems for sending and receiving
faxes.
Cyclic Redundancy Checking (CRC)
An error-detection technique consisting of a cyclic algorithm
performed on each block or frame of data by both sending and
receiving modems. The sending modem inserts the results of its
computation in each data block in the form of a CRC code. The
receiving modem compares its results with the received CRC
code and responds with either a positive or negative acknowl-
edgment. In the ARQ protocol implemented in USRobotics high
speed modems, the receiving modem accepts no more data until
a defective block is received correctly.
Data Communications
A type of communications in which computers and terminals are
able to exchange data over an electronic medium.
Data Compression Table
A table of values assigned for each character during a call under
data compression. Default values in the table are continually
altered and built during each call: the longer the table, the more
efficient throughput gained.
If a destructive Break is sent during a call (see the & Y com-
mand), causing the modems to reset the compression tables, you
can expect diminished throughput.
G-4 Glossary
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